The invention pertains to monitor circuits for rechargeable multicell battery packs.
Rechargeable batteries are widely used in standby power applications to provide temporary service during power outages and the like. Typical applications are to industrial emergency lighting systems, fire alarm systems, burglar alarms and computer systems. Because it is extremely important that the batteries operate reliably when called upon, monitor circuits are often employed for monitoring their condition and for providing an indication of any battery malfunction, should that occur. These monitor circuits normally merely sense the battery output voltage to detect when it falls below a given value. However, this is often not an accurate measure of battery condition since the output voltage of rechargeable batteries varies with such factors as temperature, load and age. In particular individual battery cells may be in a partially or completely deteriorated condition and yet not sufficiently affect the output voltage so as to be detectable by conventional circuits.